Friable compositions and process for producing same

ABSTRACT

Friable compositions suitable for use as extrusion aids in polymeric extrusion formulations are prepared by a process which comprises mixing a paraffinic hydrocarbon wax, calcium hydroxide and a fatty acid while heating to a temperature of at least 150° C and thereafter cooling to recover a solid, glass-like, friable composition, said paraffinic hydrocarbon wax having a drop melting point of at least 110° F, an oil content of not greater than 50 percent by weight and a needle penetration value (77° F) in the range of 1 mm to 20 mm, and said fatty acid being a C 16  -C 24  aliphatic hydrocarbon monocarboxylic acid or mixtures thereof.

This is a division of application Ser. No. 465,950, filed May 1, 1974,now U.S. Pat. No. 3,883,362 which in turn is a continuation-in-part ofSer. No. 425,379, filed Dec. 17, 1973, now abandoned.

This invention relates to a process for preparing a composition fromparaffinic hydrocarbon waxes, calcium hydroxide, and certain fatty acidswhich are solid, glass-like and friable at ambient conditions. Thecompositions can be ground or otherwise reduced to discrete particleshaving less tendency to fuse or coalesce than the paraffinic hydrocarbonwaxes but can be used as extrusion aids in thermoplastic formulations asthey begin to become fluidized under elevated temperatures of the orderof 100° C or higher.

Polyvinyl chloride and other thermoplastic extrusion formulationscommonly include paraffinic hydrocarbon waxes and calcium salts ofcertain fatty acids such as calcium stearate as extrusion aids. Sincethe extrusion formulations are generally fed to an extruder as a mixtureof particulate solids, it is desirable that any additives to theformulations, including the abovementioned extrusion aids, be in adiscrete solid, particulate form and capable of being handled as solids.While the calcium salts present no difficulties along this line onlycertain high quality paraffinic hydrocarbon waxes can be used.Relatively soft waxes or those of a less pure nature containingquantities of oils or other solvents are generally unacceptable from amaterials handling viewpoint; e.g., they may not form discreteparticulate solids or they may not sufficiently retain such physicalform on storage or both. As a result, a great many paraffinichydrocarbon waxes are excluded from use with thermoplastic formulationsalthough if it were not for their lack of materials handling capabilitythey would be suitable extrusion aids in such formulations.

In accordance with this invention, there is provided a process forpreparing a composition embodying both paraffinic hydrocarbon waxes andcalcium salts wherein the calcium salts are formed in situ from calciumhydroxide and certain fatty acids which composition is solid, glass-likeand friable at ambient temperaures and can be ground or otherwisereduced to discrete particulate form having reduced tendency to fuse orcoalesce on standing than the paraffinic hydrocarbon waxes bythemselves. The composition still begins to become fluidized at elevatedtemperatures; e.g., 100° C, thus rendering them suitable for extrusionoperations. This invention, therefore, provides a process for renderingrelatively soft, amorphous waxes, or those of a less pure nature,suitable for solids handling situations such as with thermoplasticextrusion formulations. Further, when the compositions produced by thisprocess are used in thermoplastic extrusion formulations, there is anadded benefit in that a single material provides both the paraffinichydrocarbon wax requirement as well as the calcium salt requirement.Quite obviously, the invention is applicable to higher quality harderwaxes as well.

It is emphasized at the outset that the composition prepared with theprocess of this invention is not a mere physical blend wherein eachcomponent contributes its individual properties without any interactionwith each other. Rather, the physical form of the composition is unlikeeither of the individual components. The composition is bestcharacterized as being a glass-like, friable solid at ambient conditionsand might be described as resulting from a synergistic action betweenthe components. From a physical chemistry standpoint, it is not knownwhat actually occurs in forming the composition although some of thoseskilled in the art might make analogy to the grease art.

Broadly, the process of the invention comprises mixing paraffinichydrocarbon wax, calcium hydroxide and certain fatty acids while heatingthe mixture to at least about 150° C, preferably at least 180° C, andthereafter cooling and recovering the solid, glass-like, friablecomposition.

The fatty acids which may be employed are the C₁₆ -C₂₄ aliphatichydrocarbon monocarboxylic acids or mixtures thereof. These acids may besaturated or unsaturated. When mixtures of the acids are used, they maycontain up to about 15 weight percent of a C₁₄ aliphatic hydrocarbonmonocarboxylic acid of the same saturation characteristics outlinedabove. Illustrative of suitable acids are palmitic, stearic, oleic,linoleic, eicosanic, behenic, tall oil fatty acid, hydrogenatedvegetable fatty acid, hydrogenated tallow fatty acid, distilledcottonseed fatty acid, and the like. Various commercial grades ofsuitable acids are available, some of which are listed in Fatty Acidsand Their Industrial Applications by E. S. Pattison, 1968, at Page 7,Table 1-2 (excluding high lauric). These suitable commercial acids aregenerally mixtures of the acids hereinbefore described and mayadditionally have small amounts of certain impurities depending on theirmethod of manufacture.

The calcium hydroxide employed may be any commercial grade material suchas slaked lime or hydrated lime.

The suitable paraffinic hydrocarbon waxes are generally derived frompetroleum sources. These waxes contain a variety of hydrocarbonstructures, for example normal paraffins, isoparaffins, cycloparaffins,small quantities of polycyclo-paraffins and aromatics and otherhydrocarbons, and may be in a purified form or may contain oilsdepending upon their source and/or manner of recovery. The paraffinichydrocarbon waxes which are particularly useful are those having a dropmelting point (ASTM D127-63) of at least 110° F, preferably at least145° F, an oil content (ASTM D721-65T) of not greater than 50 weightpercent, preferably not greater than 20 weight percent, and a needlepenetration value at 77° F (ASTM D1321-65) in the range of 1 mm to 20mm, preferably 1 mm to 10 mm.

More specifically, the process of the invention may be carried out bycharging the paraffinic hydrocarbon wax, calcium hydroxide and fattyacid to a heated vessel equipped with an agitator. The wax may bepre-melted before being charged or it may be melted in the vessel. Thefatty acid may be handled likewise as appropriate. The calciumhydroxide, being a solid, may be charged using any convenient solidshandling means such as an auger.

While the sequence of addition is not critical insofar as the inventionis concerned, some advantages may arise by initially providing a moltenwax in the vessel followed by addition of the solid calcium hydroxide.After the calcium hydroxide particles have been thoroughly dispersed bythe vessel agitator the fatty acid, in liquid form, may be metered intothe vessel. On the other hand, the fatty acid may be added prior to thecalcium hydroxide. In either manner the rate of production of water,through reaction of the calcium hydroxide and fatty acid, may be easilycontrolled. This has significance for the reason that the processinvolves temperatures above the boiling point of water and consequentlyany water present or produced becomes vaporized and tends to cause somefoaming of the mixture. Of course, any instance wherein foaming becomesa problem may be overcome by employing suitable equipment as is known inthe art.

In any event, the mixture of materials are heated wih agitation to atleast 150° C. Heating of the materials may continue while they are beingadded to the vessel. Generally speaking, the temperature of 150° C willnot be achieved until after all of the materials have been added. It ispreferred to heat the mixture to at least 180° C as this hastens thetransformation of the mixture into the desired composition.

The transformation of the mixture may best be described as follows: themolten wax initially provides a continuous liquid phase in which thecalcium hydroxide and fatty acid react in situ to provide the calciumsalt and water. The calcium salt, being an insoluble solid, becomesthoroughly dispersed as particles throughout the wax while the water,for the most part, appears to be vaporized from the mixture. As heatingof the mixture continues, there is an increase in viscosity. The massfirst reaches a homogenous paste-like consistency and thereafter becomespoint that the final temperature as hereinbefore noted will be reachedand the composition is formed. Heating may be continued for a shortperiod of time to insure completion of the transformation, even tohigher temperatures short of degradative temperatures.

The hot mass is then removed from the vessel and cooled to ambientconditions whereupon the composition becomes a solid, glass-like friablematerial which can be ground or otherwise reduced to a particular formwhich substantially retains its discreteness and integrity. While thecomposition is a solid at ambient conditions and can be easily fracturedor chopped at these conditions, it is perhaps more convenient andsomewhat easier to grind the composition under cryogenic conditions. Ineither situation, the resultant particulate composition at ambientconditions can be easily handled with conventional solids handlingequipment. Further, the particulate composition substantially maintainsits integrity upon standing or being stored.

Generally, the process of this invention will employ a mol ratio ofcalcium hydroxide to fatty acid in the range of 0.5/1 to 1/1 and aweight ratio of wax to fatty acid in the range of 0.5/1 to 2/1. It ispreferred that the mol ratio of calcium hydroxide to fatty acid be0.55/1 to 0.65/1 and the weight ratio of wax to fatty acid be 0.9/1 to1/1.

It is also possible to incorporate other additives into the compositionssuch as when they are employed as extrusion aids or lubricants. In theseinstances, other processing aids such as polyethylene waxes or acrylatepolymers may be included, pigments such as TiO₂, fillers, and evenreinforcing materials may be included.

The invention will be further illustrated by the following examples.

EXAMPLE 1

A Hobart mixer equipped with an electric heating mantel was charged withabout 255 g of paraffinic hydrocarbon wax (Code 776) and about 281 g ofstearic acid (industrial grade, Humko Industrene R). The wax had anaverage drop melting point of about 148° F, an average oil content ofabout 16 weight percent, and an average needle penetration value (77° F)of about 8.1 mm. With heating these materials were melted and then about44 g of solid calcium hydroxide were added. With continuous agitationand heating, the temperature rose to about 180° C during which time themixture was observed to pass through the phases described hereinbeforein the specification. The resulting product formed a ball on theagitator blade and was noted to be a homogenous, taffy-like material.Heating of the product was continued at temperatures of 180° C-210° Cfor an additional forty minutes. Upon cooling to ambient conditions, theproduct became hard and friable, very unlike the starting wax.

EXAMPLE 2

The process of Example 1 was repeated except that 37 g of solid calciumhydroxide were employed and the subsequent heating was not employed. Thesame results were achieved and while the product at ambient conditionswas hard and friable, it was noted that it did not ball up on theagitator blade prior to cooling.

EXAMPLE 3

A further run was carried in accordance with the procedure of Example 2except that 55 g of solid calcium hydroxide were employed. The finalproduct was much like that of Example 1.

EXAMPLE 4

An additional run was carried out as described in Example 2 except that74 g of solid calcium hydroxide were employed. A product comparable tothose in the previous examples was obtained.

EXAMPLE 5

A further run was carried out using a procedure as described in Example2 except that the following were employed: 255 g of a paraffinichydrocarbon wax (Citcon Code 784) having an average drop melting pointof about 165° F, an average oil content of about 3 weight percent and anaverage needle penetration value (77° F) of 1.5 mm; 280 g of acommercial grade double pressed stearic acid (Thompson-Heyward); and 47g calcium hydroxide. The materials were heated to 190° C-200° C. Thefinal product was much like that of Example 1.

EXAMPLE 6

A run was also carried out with the procedure described in Example 2except that the materials employed were 300 g of a paraffinichydrocarbon wax having an average drop melting point of about 148° F, anaverage oil content of about 16 weight percent and an average needlepenetration value (77° F) of about 8.1 mm; 181 g tall oil fatty acid(Hercules Panak 985); and 44 g calcium hydroxide; and the materials wereheated to about 190° C. The final product was similar to that of Example1.

EXAMPLE 7

Similar results may be achieved using the process of Example 1substituting palmitic acid or mixtures thereof with oleic acid.

EXAMPLE 8

A further run was carried out using a procedure generally as describedin Example 1 except that a Ross mixer was used. About 2822 g ofparaffinic hydrocarbon wax (Code 776) and about 1760 g of hydrogenatedtallow fatty acid (Darling DAR-C) were charged and melted together whileheating to about 150° C at which temperature 317 g of hydrated lime (AshGrove Kemilime) were incrementally added over a period of 17 minuteswith constant stirring. The wax had an average drop melting point ofabout 148° F, an average oil content of about 16 weight percent, and anaverage needle penetration value (77° F) of about 8.1 mm. During thisperiod, the temperature rose to 188° C and the mixture was observed topass through the phases described hereinbefore in the specification. Theresulting product formed a ball on the agitator blade and was noted tobe a homogenous, taffy-like material. Heating was continued attemperatures of 188° C to 195° C for an additional 25 minutes. Uponcooling to ambient conditions, the product became hard and friable.

EXAMPLE 9

To demonstrate the unique ability of the compositions prepared by theprocess of this invention to retain their discreteness compared tocommercial wax used as an extrusion aid in PVC formulations two testswere run as follows:

20 g of a powdered sample (all of which pass a USS 30 mesh sieve) wereplaced in a 100 ml graduated cylinder (2.5 cm diameter). The loosevolume was noted and a weight was placed on top and the initialcompacted volume was noted. The sample was allowed to stand under weightfor 1 hour at room temperature and the volume was again noted. Thesample was then placed in an oven maintained at 60° C for 1 hour and thevolume was again noted.

The particulars of each run together with the results are indicated inthe table.

                  TABLE                                                           ______________________________________                                                      VOLUME MEASUREMENTS (ml)                                                                       Room                                                                          Temper-                                        Run   Weight            Ini-   ature   60° C                           No.   (g)      Loose    tial   1 Hr    1 Hr                                   ______________________________________                                        1.sup.a                                                                             250      53       45     42      33.sup.c                               2.sup.b                                                                             250      57       50     47      43                                     ______________________________________                                         .sup.a Commercial paraffinic wax used in the thermoplastic formulations a     extrusion aid, Aristowax X1-165.                                              .sup.b Composition prepared by process of invention according to Example      using 3481 g wax, 3638 g Thompson-Heyward double pressed stearic acid and     612 g calcium hydroxide.                                                      .sup.c Sample fused to a solid cake.                                     

As indicated hereinbefore, the compositions of this invention aresuitable for use as extrusion aids in polymer formulations intended forprocessing by extrusion. These compositions not only provide therequirements of both the heretofore separately employed waxes and fattyacid salts but they also do not suffer from dusting problems when dryblended into extrusion formulations.

Thus having described the invention in detail, it will be understood bythose skilled in the art that certain modifications and variations maybe made without departing from the spirit and scope of the invention asdescribed herein and defined in the appended claims.

We claim:
 1. In an improved process for the extrusion processing of athermoplastic polymer formulation using extrusion aids which are addedto said thermoplastic polymer formulation prior to carrying out saidextrusion, the improvement comprising utilizing an extrusion aid whichis friable at ambient temperatures, prepared by mixing a paraffinichydrocarbon wax, calcium hydroxide and a fatty acid while heating to atemperature of at least 150° C and thereafter cooling to recover a solidglass-like, friable composition, said paraffinic hydrocarbon wax havinga drop melting point of at least 110° F, an oil content of not greaterthan 50 percent by weight and a needle penetration value (77° F) in therange of from 1 millimeter to 20 millimeters, and said fatty acid beinga C₁₆ -C₂₄ aliphatic hydrocarbon monocarboxylic acid or mixturesthereof.
 2. The invention of claim 1 wherein the calcium hydroxide ismixed with the paraffinic hydrocarbon wax prior to adding the fattyacid.
 3. The invention of claim 1 wherein the mol ratio of calciumhydroxide to fatty acid is in the range of 0.5/1 to 1/1.
 4. Theinvention of claim 3 wherein the mol ratio is 0.55/1 to 0.65/1.
 5. Theinvention of claim 3 wherein the weight ratio of wax to fatty acid is inthe range of 0.5/1 to 2/1.
 6. The invention of claim 4 wherein theweight ratio of wax to fatty acid is 0.9/1 to 1/1.
 7. The invention ofclaim 1 wherein the paraffinic hydrocarbon wax has a drop melting pointof at least 145° F, an oil content of not greater than 20 weight percentand a needle penetration value at 77° F in the range of 1 mm to 10 mm.8. The invention of claim 7 wherein the fatty acid is palmitic acid,stearic acid, oleic acid, linoleic acid, tall oil fatty acid, eicosanicacid, behenic acid, or mixtures thereof.
 9. The invention of claim 1wherein a mixture of fatty acids is employed.
 10. The invention of claim9 wherein the mixture of fatty acids contains up to 15 weight percent ofa C₁₄ aliphatic hydrocarbon monocarboxylic acid.
 11. The invention ofclaim 1 wherein the composition is prepared by mixing the fatty acidwith the paraffinic hydrocarbon wax prior to adding the calciumhydroxide.